Is there a time limit for how long offline responses are stored?

Some of our participants are using the offline link to complete surveys and forgot to upload their responses when they were done taking their survey. When they returned to the dashboard to upload their responses, none of their responses had been saved. Is there a time limit on how long responses are stored in the offline option?

Also, some of these participants mentioned that they had used the offline survey link while still connected to the internet. Would that have affected how their responses were stored?